3 Answers
3

For the bottom, you need to install a (or replace the existing) door bottom (Yeah, someone was really inventive with that name). The thing goes on the bottom of the door and will fill the gap there.

There are 2 general types, ones with vinyl fins (like this) or ones with short brushes (like this). I personally find the latter work better, though if you have a large gap, the brush type may not be long enough to fill the gap fully, though a gap that large likely means your threshold is improperly sized.

The "door bottom" is sometimes referred to as a "door sweep."
–
BMitch♦Dec 5 '12 at 20:28

3

And for the perimeter. Doors often warp some, so that the original weather stripping no longer makes contact everywhere. Or the rubber hardens, losing it's ability to even contact the door. In either case, adding cheap stick on foam weather stripping will stop drafts from the perimeter. At least for a few years until the foam breaks down. By then, you've probably moved.
–
bcworkzDec 5 '12 at 22:50